A time fidelity control foundation for hierarchical discrete-event systems

Ngo, Quang Ha; Seow, Kiam Tian

doi:10.1109/coase.2014.6899363

2014 IEEE International Conference on Automation Science and Engineering (CASE) 2014

DOI: 10.1109/coase.2014.6899363

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A time fidelity control foundation for hierarchical discrete-event systems

Quang Ha Ngo

Kiam Tian Seow

Abstract: In the existing paradigm of formal languages and finite automata, the hierarchical control setup for untimed discrete-event systems (untimed DES's) is a standard high-level command and low-level control structure, and timed DES's (TDES's) can be modeled by a class of automata called timed transition graphs (TTG's) incorporated with time fidelity. In this paper, using the same hierarchical control setup, with the TDES at the low level modeled by a Moore TTG with time fidelity, supporting concepts are proposed f… Show more

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“…Section 4 defines the constituent concepts for the system concept of timed output-control consistency, by which the system abstraction at the high level possesses a natural timed control structure as the system at the low level. An earlier version of the work in Section 4 was published in (Ngo and Seow, 2014b); the concepts are more fully developed in this paper. Together with these constituent concepts, Section 5 adds a timed concept of partner-freeness to formulate system sufficiency structures for hierarchical consistency between the two levels, without and with output-time fidelity guarantee.…”

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A hierarchical consistency framework for real-time supervisory control

Ngo

Seow²

2018

Discrete Event Dyn Syst

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The control framework of hierarchical consistency of timed discrete-event systems (TDES's) is investigated in a standard two-level hierarchy. Real-time concepts and the associated theoretical results supporting consistent TDES hierarchies are developed. Where the given low-level system model of the hierarchy possesses time fidelity, a consistency version that assures time fidelity of the high-level system model is also developed. Importantly, this version furnishes a sound real-time high-level specification design foundation for hierarchical control. An example illustrates the new time-fidelity control foundation. Given that in general, a given two-level TDES hierarchy is not hierarchically consistent between the levels, the structural existence and synthesis of the sufficiency structure for hierarchical consistency is investigated. Both the timed versions of hierarchical consistency -without and with output-time fidelity guarantee -are successively treated. The abstraction or output-system refinement procedures for the version without output-time fidelity guarantee are first developed for a class of TDES hierarchies under mild output-system design restrictions. The abstraction methods for the version with output-time fidelity are then developed for a subclass 'linearly' structured under further output-system design restrictions. A detailed example explains and illustrates the use of an overarching method developed.Keywords Hierarchical control ¨timed discrete-event systems ¨formal languages ¨finite automata. IntroductionUnder the general framework of formal languages and finite (or finite-state) automata, the seminal concept of hierarchical consistency for logical or untimed discrete-event systems (DES's) (Zhong and Wonham, 1990) is suitably extended to timed DES's (TDES's) in this paper. In a two-level, untimed hierarchical control setup, conceptualized in (Zhong and and algorithmically realized in (Ngo and Seow, 2014a), the system at the low level drives the system at the high level which is an abstraction of the former, via an information channel modeled by a hierarchical reporter map. Depicted in Fig. 1, this setup consists of two horizontal levels of standard feedback control which are vertically interconnected so that a manager at the high level (or high-level supervisor) can issue commands to an operator at the low level (or low-level supervisor) to control a real DES modeled by a Moore automaton (Eilenberg, 1974), in response to information of interest sent up from the low level to the high level. By hierarchical consistency between the levels (Zhong and , a low-level supervisor implementing feasible commands issued (or virtual controls) at the high level can fully realize a controllable prefix-closed specification task (Ramadge and Wonham, 1987) prescribed at the high level. The importance of hierarchical control stems from the fact that, in general, a hierarchical structure conforms better to practice and renders a given system more manageable for system specification and control in terms of large-sca...

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A hierarchical consistency framework for real-time supervisory control

Ngo

Seow²

2018

Discrete Event Dyn Syst

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A time fidelity control foundation for hierarchical discrete-event systems

Cited by 1 publication

References 8 publications

A hierarchical consistency framework for real-time supervisory control

A hierarchical consistency framework for real-time supervisory control

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